--- Turbo Timer ON, Key OUT, Fans ON ---
========================================
[Acknowledgements]
- This was written in testament to the power of these forums. It was an idea
that someone with very little / no electrical knowledge had and wanted to
know if it could be done (and so started a thread asking about it).
-
Thanks go out to
(luv2rallye) for implementation improvements and some
last minute sanity checks.
[Requirements]
- Properly Installed Turbo Timer
- Crimps / Splices / Solder Equipment
- Automotive Relay
- 1N7003 Diode (or 12v Automotive Relay with built-in flyback protection)
- Relay Harness
or
- Female Blade Connectors & 16AWG multi-strand wire (or larger)
[Directions]
- Prepare the relay harness by first splicing a 1N7003 diode between pins
85 & 86 of the Automotive Relay. If the relay you are using already has
built-in flyback protection, skip this step.
> Make sure the "negative" part of the diode (marked with a band)
attaches to pin 86.
> If using a relay with built-in flyback protection, double-check the polarity
of the connections to ensure the "negative" part of the diode connects
to +12v source, else risk destroying the relay. Most relays will have a
schematic imprinted on the side clearly indicating the polarity of the
internal diode (If not, research how to test diodes with a multi-meter,
as that is outside the scope of this article).
- Disconnect the negative (-) terminal of the battery.
- Locate a suitable place to install the relay.
> Up under the steering column, dash, or center console would be
a good place to start.
- Locate pin-20 of the ECU (Behind driver center kick panel).
- Locate pin-3 of the Key Reminder Switch (Underneath steering column).
- Splice a wire into pin-20 of the ECU and connect it to pin-87 of the relay.
- Splice a wire into pin-3 of the Key Reminder Switch and connect it to pin-86
of the relay.
- Connect pin-85 and pin-30 of the relay together and attach to a suitable
ground point.
- Double-check all work.
- Reconnect the negative (-) terminal of the battery and test the final product.
[Theory of Operation]
- When the ignition key is removed from the cylinder, pin-3 of the
Key Reminder Switch is connected to pin-7 of the Key Reminder Switch which
provides a constant +12v.
- This +12v will energize the grounded coil of the installed relay, thus
activating the internal switch.
- Once activated, pin-20 of the ECU will be grounded. This will activate both the
Radiator and Condenser Fans in HI mode while the engine is still running
(provided by the turbo timer).
- When the turbo timer removes power from IG1, IG2, ACC (The ignition
circuits), the radiator fans will turn off.
- Inserting a key to start the engine will break contact between pins 3 & 7
of the Key Reminder Switch and return activation of the fans back under
control of the ECU.
> Keep this in mind if using a remote start feature - the fans WILL turn
on when started with this mod as-is.
[Notes]
- Transistors and ICs must be protected from the brief high voltage 'spike' produced
when the relay coil is switched off. Connecting the protection diode 'backwards'
so that it will normally NOT conduct achieves this. Conduction will only occur when
the relay coil is switched off and it is at this moment that current tries to
continue flowing through the coil, but is harmlessly diverted through the diode.
Without the diode, no current could flow and the coil would produce a damaging high
voltage 'spike' as the magnetic field collapses.
> More info: (
Relays)
> More info: (
Installing Relays or Solenoids(read this))
- It has been brought to my attention that the wiring for stock 2g fans actually supports
three (3) different speeds (LO, MED, HI). Each fan has two power feeds and two grounds.
However, this should only be of real concern to those who are still running stock fans
because when wiring up most aftermarket fans (single speed), the two power feeds and
two ground feeds for each fan are normally tied together. If this is the case, some
additional wiring (and research) may be needed to retain the stock functionality of
the fans as it is outside the scope of this article.
> LO Circuit Activated -- LO speed
> HI Circuit Activated -- MED speed
> LO & HI Circuits Activated -- HI speed
* Cond LO Circuit (Automatic Compressor ECM provides +12v to Cond LO Relay coil)
* Rad LO Circuit (ECU-21 grounded)
* Rad & Cond HI Circuit (ECU-20 grounded)
[Disclaimer]
- The preceeding modifications were designed with a 1997 5-speed GST in mind
and *should* work on the turbo A/T setups as well as the 2.4L setup. This
will not work on the N/T 2G's.
- If in doubt, ask (read: research)!